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Interdelivery Interval and Risk of Symptomatic Uterine> <Rupture>
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Thomas D. Shipp, MD,a Carolyn M. Zelop, MD,b John T. Repke, MD,c Amy
--
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Cohen,d and Ellice Lieberman, MD, DrPHd
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Objective: To relate interdelivery interval to risk of <uterine>
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<rupture> during a trial of labor after prior cesarean delivery.
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Methods: We reviewed the medical records of all women who had a trial of
labor after cesarean delivery over 12 years (July 1984 to June 1996).
Analysis was limited to women with only one prior cesarean delivery and
no prior vaginal deliveries who delivered term singletons and whose
medical records included the month and year of the prior delivery. The
time in months between the prior cesarean delivery and the index trial
of labor was calculated, and the women were divided accordingly to
permit comparison with respect to symptomatic <uterine> <rupture>.
Results: Two thousand four hundred nine women had trials of labor after
one prior cesarean delivery and had complete data from the medical
records. There were 29 <uterine> <ruptures> (1.2%) in the population.
For interdelivery intervals up to 18 months, the <uterine> <rupture>
rate was 2.25% (seven of 311) compared with 1.05% (22 of 2098) with
intervals of 19 months or longer (P = .07). Multiple logistic
regression was used to assess the risk of <uterine> <rupture> according
to interdelivery interval while controlling for maternal age, public
assistance, length of labor, gestational age at least 41 weeks, and
oxytocin use. Women with interdelivery intervals of up to 18 months
were three times as likely (95% confidence interval, 1.2, 7.2) to have
symptomatic <uterine> <rupture>.
Conclusion: Interdelivery intervals of up to 18 months were associated
with increased risk of symptomatic <uterine> <rupture> during a trial of
labor after cesarean delivery compared with that for longer
interdelivery intervals.
aDepartment of Obstetrics and Gynecology, Massachusetts General
Hospital, Harvard Medical School, Boston, Massachussetts, USA
bDepartment of Obstetrics and Gynecology, Lenox Hill Hospital, New York,
New York, USA
cDepartment of Obstetrics and Gynecology, University of Nebraska Medical
Center, University of Nebraska, Omaha, Nebraska, USA
dDepartment of Obstetrics and Gynecology, Brigham and Women's Hospital,
Harvard Medical School, Boston, Massachussetts, USA
(Obstet Gynecol 2001:97:175-177. © 2001 by The American College of
Obstetricians and Gynecologists.)
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The most serious complication of trial of labor after cesarean delivery
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is the risk of symptomatic <uterine> <rupture>. Overall, the risk of
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<uterine> <rupture> during trial of labor is approximately 1%.1 Certain
subgroups of parturients have been identified as being at higher risk of
<uterine> <rupture>, including those with multiple prior cesarean
deliveries2,3 and induction with oxytocin.4 There might be other
subgroups that are also at increased risk of <uterine> <rupture> during
a trial of labor after cesarean delivery. We evaluated interdelivery
interval in this regard.
Materials and Methods
The medical records of all women admitted to Brigham and Women's
Hospital for trials of labor after cesarean delivery over 12 years (July
1984 to June 1996) were reviewed. Specific findings were reported
previously.1,5 Our data set included the month and year of the prior
cesarean delivery. The current analysis was limited to women with one
prior cesarean delivery and no previous vaginal deliveries. We included
only women who delivered singletons at term and whose medical records
included the month and year of the prior delivery. Of 2825 records, 416
lacked adequate information regarding the date of the prior delivery,
leaving 2409 for the present analysis.
<Uterine> <rupture> was defined as complete disruption of the cesarean
scar with at least one of the following symptoms: hemorrhage, need for
hysterectomy, bladder damage, extrusion of any portion of the fetus or
placenta from the uterus, or cesarean delivery for nonreassuring fetal
status or suspected <uterine> <rupture>. Asymptomatic uterine
dehiscences were not included because they were not associated with
maternal or neonatal morbidity.
The frequency of <uterine> <rupture> was related to the interdelivery
interval. The interdelivery interval, calculated as the time in months
between the index trial of labor and the prior delivery, was categorized
as up to 18 months and 19 months or more. Demographic data, clinical
characteristics, and <uterine> <rupture> rates were compared for the
groups. Statistical significance was assessed using 2 for categoric
variables or Fisher exact test, as appropriate; continuous variables
were compared with Student t test. P < .05 was considered statistically
significant. Multiple logistic regression analysis was used to assess
the association of interdelivery interval with <uterine> <rupture>,
while controlling for potential confounding factors.
Results
Two thousand four hundred nine women had trials of labor after one prior
cesarean delivery and had the indicated date of the prior delivery noted
in the medical record. There were 29 <uterine> <ruptures> (1.2%) for
the entire population. The rupture rate was 2.25% (seven of 311) for
women with an interdelivery interval of up to 18 months and 1.05% (22 of
2098) for women with intervals of 19 months or more; this difference was
not statistically significant (P = .07).
Demographic and clinical characteristics of both groups were compared
(Table 1). Women with shorter interdelivery intervals were on average
younger (mean 28.5 years versus 31.4 years) and were more likely to be
receiving public assistance (19.3% versus 12.7%). They were also less
likely to have a gestational age of at least 41 weeks (16.7% versus
21.8%).
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The characteristics of women with and without <uterine> <rupture> were
compared (Table 2). Women with <uterine> <rupture> were more likely to
have had labor induced with oxytocin and were on average 2.6 years older
than women without <uterine> <rupture>. Because older women were also
more likely to have a longer interdelivery interval (which is associated
with a lower <uterine> <rupture> rate), maternal age represented a
potentially important confounder of the association between
interdelivery interval and <uterine> <rupture>.
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--------------------------------------------------------------------------------
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To control for such potential confounding, multiple logistic regression
analysis was done. In that model, we assessed the risk of <uterine>
<rupture> for women with interdelivery intervals of up to 18 months,
compared with those 19 months or more, while controlling for the
potential confounding factors of maternal age, public assistance, length
of labor, gestational age of at least 41 weeks, and induction or
augmentation of labor with oxytocin. After controlling for this
confounding, short interdelivery interval was a significant predictor of
<uterine> <rupture>. Women with interdelivery intervals of up to 18
months had an odds ratio (OR) of 3.0 (95% confidence interval [CI], 1.2,
7.2) for a symptomatic <uterine> <rupture> (Table 3).
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Discussion
Our data indicate that among women with one prior cesarean delivery who
then have a trial of labor, the risk of <uterine> <rupture> may be
higher for women with interdelivery intervals of up to 18 months. This
correlates with an interpregnancy interval of approximately 9 months or
less, because we included only women with term gestations in the index
pregnancies. Women who have such short interdelivery intervals have a
threefold increased risk of <uterine> <rupture> during a trial of labor
after cesarean delivery. Although the crude association did not reach
statistical significance (P = .07), this resulted from substantial
confounding by maternal age. Older women were more likely to have had
<uterine> <rupture> and more likely to have had longer interdelivery
intervals. Multivariate analyses were needed to control for these
imbalances, and after adjustment there was a significant association of
interdelivery interval with <uterine> <rupture>. The risk of <uterine>
<rupture> with interdelivery intervals of 19 months or more did not vary
according to the time from prior cesarean delivery and remained constant
at approximately 1%.
One possible explanation for our findings is incomplete healing of the
uterine scar from the previous cesarean delivery. Healing of the
hysterotomy has been evaluated by magnetic resonance imaging (MRI).6 The
zonal anatomy of the uterine hysterotomy site from uncomplicated low
transverse incisions was restored by 6 months postpartum as evaluated by
MRI. Complete involution of the uterus and restoration of uterine
anatomy required at least 6 months and possibly 9 months.6 We
hypothesized that pregnancy occurring within this relatively short
period postpartum, before complete uterine healing, might be associated
with an increased risk of <uterine> <rupture> during a subsequent trial
of labor after cesarean delivery. Therefore, by defining our short
interdelivery interval as deliveries at term with interdelivery
intervals of 18 months or less, the higher rate of <uterine> <rupture>
in this subgroup might be from incomplete healing of the prior
hysterotomy site.
It was not known whether the hysterotomy site healed by regeneration of
the myometrium or through the more common means of scar formation. Some
investigators have argued for the former because of the frequent failure
to identify the prior cesarean delivery wound during subsequent surgery.
However, pathologic review of a recent cesarean delivery wound that was
incompletely healed found the presence of granulation tissue and
fibrosis, suggesting scar formation.7 A rat model developed to assess
the strength of uterine wound healing8 might prove helpful for further
investigations.
Despite the frequent use of a trial of labor after cesarean delivery,
there is little information regarding the effect of short interdelivery
interval on <uterine> <rupture> after prior hysterotomy. A
first-trimester rupture of a prior classical cesarean incision has been
described in a woman with an interpregnancy interval of approximately
four months.9 In a cohort of women who had pregnancy termination by
hysterotomy and then a subsequent pregnancy after a short interval, with
42% having an interval of 6 months or less and 58% 1 year or less, there
were three <uterine> <ruptures> (7.9%) or impending ruptures in 38 women
with pregnancies reaching the third trimester. The scars were described
as thin in 45.2% of women.10 Although prior pregnancy termination via
hysterotomy cannot be compared directly with prior cesarean delivery,
the short interpregnancy intervals could have led to incomplete healing
and therefore the higher rate of <uterine> <rupture> in subsequent
pregnancies. Further study is required to determine etiologic
mechanisms.
We did not examine the occurrence of asymptomatic dehiscences in this
study and instead focused on symptomatic ruptures. As previously
stated, we defined <uterine> <rupture> as complete disruption of the
prior incision, with associated maternal or neonatal sequelae.1,5
Asymptomatic dehiscences do not, by our definition, lead to adverse
sequelae and therefore are less clinically significant in the index
pregnancy. In addition, study of these lesions from retrospective data
is difficult because they frequently go undetected.
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References
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1. Shipp TD, Zelop CM, Repke JT, Cohen A, Caughey AB, Lieberman E.
Intrapartum <uterine> <rupture> and dehiscence in patients with prior
lower uterine segment vertical and transverse incisions. Obstet Gynecol
1999;94:735-40.
2. Leung AS, Farmer RM, Leung EK, Medearis AL, Paul RH. Risk factors
associated with <uterine> <rupture> during trial of labor after cesarean
delivery: A case-control study. Am J Obstet Gynecol 1993;168:1358-63.
3. Caughey AB, Shipp TD, Repke JT, Zelop CM, Cohen A, Lieberman E. Rate
of <uterine> <rupture> during a trial of labor in women with one or two
prior cesarean deliveries. Am J Obstet Gynecol 1999;181:872-6.
4. Zelop CM, Shipp TD, Repke JT, Cohen A, Caughey AB, Lieberman E.
<Uterine> <rupture during induced or augmented labor in gravid women
with one prior cesarean delivery. Am J Obstet Gynecol 1999;181:882-6.
5. Caughey AB, Shipp TD, Repke JT, Zelop C, Cohen A, Lieberman E. Trial
of labor after cesarean delivery: The effect of previous vaginal
delivery. Am J Obstet Gynecol 1998;179:938-41.
6. Dicle O, Kucukler C, Pirnar T, Erata Y, Posaci C. Magnetic
resonance imaging evaluation of incision healing after cesarean
sections. Eur Radiol 1997;7:31-4.
7. Wojdecki J, Grynsztajn A. Scar formation in the uterus after
cesarean section. Am J Obstet Gynecol 1970;107:322-4.
8. Schlaff WD, Cooley BC, Shen W, Gittlesohn AM, Rock JA. A rat
uterine horn model of genital tract wound healing. Fertil Steril
1987;48:866-72.
9. Lazarus EJ. Early rupture of the gravid uterus. Am J Obstet
Gynecol 1978;132:224.
10. Clow WM, Crompton AC. The wounded uterus: Pregnancy after
hysterotomy. BMJ 1973;1:321-3.
Address reprint requests to: Thomas D. Shipp, MD, Department of
Obstetrics and Gynecology, Massachusetts General Hospital, Founders 430,
Fruit Street, Boston, MA 02114, E-mail: tshipp@partners.org
Received June 7, 2000.
Received in revised form September 28, 2000.
Accepted October 12, 2000.
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Copyright © 2001 by The American College of Obstetricians and
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Gynecologists
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Published by Elsevier Science Inc.
Visit Obstetrics & Gynecology online at http://www.greenjournal.org
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At Sat, 01 Jun 2002, Bernard Cristalli wrote:
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>
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>Hi listmates,
>
>Do any of you have data regarding the delay that should (must) be imposed to
>women before being pregnant again after a previous C-section.
>My understanding is that some months are recommended but it appears
>unsupported by data.
>Am I wrong?
>What do you, colleagues do?
>
>--
>Bernard Cristalli MD AMACOG
>AIHP - ACCA
>Paris France
>Bernard.Cristalli@CliniquedelEssonne.fr
>http://www.CliniquedelEssonne.fr
>http://www.obgyn.net/corresp/cristalli.htm
>http://www.gyneweb.fr
>'64 Mk2 3.8
>
--
"Life is neither the notes nor the silence between the notes, but the music that
arises out of sound and silence felt as a living whole. Stop choosing...between
chaos and order, and live at the boundary between them, where rest and action
move together..." David Whyte
